1963 -- Martin Luther King, Jr. wrote his "Letter from Birmingham Jail while incarcerated in Alabama for protesting against segregation.
Also related to non-violent protesting ...
1919 -- Gandhi organized a day of prayer and fasting in response to the British slaughter of Indian protesters in the Amritsar Massacre.
1862 -- A bill ending slavery in the District of Columbia becomes law.
1521 -- Martin Luther made his first appearance before the Diet of Worms (assembly for deliberation). The diet's product was the Edict of Worms, which addressed the effects of the Protestant Reformation.